Aug. 25, 2015

Mixers and Equalizers, Part II

(con't from Part I)

Compared to a pipe organ, some electronic organ stops just don't match up.  This is believed to be due in part to the effects speaker cones (drivers) in external speaker systems can have on frequency ranges in relation to the harmonics of organ stops and their contribution to organ tone.  Drivers which cause slight disturbances of reproduction in the region of those same harmonics, where certain frequencies are subdued or taken out, can greatly affect whether a stop going through that driver sounds real and authentic or whether it sounds plastic and flat.  While the subject remains controversial, experimentation with a frequency analyzer on certain drivers has shown that frequencies in the range of 1,000-2,000 Hz can get compromised, and that exaggerating this same frequency range using a graphic equalizer gives an interesting sound, without which it becomes lifeless.  Other experiments are reported to refute this claim.  The fact remains, any graphic equalizer looped into a power mixer and external speaker system of an electronic organ has to be set in a fashion that not only brings out the best in the signal coming to it, but also overcomes any deficiencies in production of the organ sound after the signal leaves it [See blog, Mixers and Equalizers, Part I].   

Good results are obtained when the frequency band width around 1KHz and both extreme ends (at 25Hz and 16KHz) of each channel of a dual graphic equalizer are boosted while the low mid range and upper ranges are reduced (See photo).  Many ways to configure these settings might present themselves, but this overall strategy has been battle tested with all types of organ music on a large electronic organ and is very solid.  It works very well.

These EQ settings may be enhanced if the power mixer happens to be equipped with its own EQ settings for the main and monitor channels.  These built-in equalizers are often of 7 bands and color the signal before it's sent to the bigger, 15 band dual graphic.  By reducing the frequencies at 250Hz, 500Hz, 2KHz, and 4KHz by -3 dB, boosting the band width at 80Hz by +3 dB, and keeping the band widths flat at 1KHz and 10KHz on the mixer's built-in equalizers, the overall results can be accentuated.